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The analysis of long-term collector samples has given information on wall erosion by ion sputtering in W7-AS. There is strong indication that this erosion occurred during high iota-discharges which are separatrix-dominated by 5/n island chains. Langmuir and calorimeter probe measurements have demonstrated that in this case particle and heat fluxes leave the plasma locally with high densities. Erosion of limiter surfaces measured post-mortem can be satisfactorily correlated with results from measurements with flush mounted limiter probes. Measurements with a moveable collector probe have shown that the plasma impurity contamination by limiter material is higher after wall boronisation in limiter-dominated discharges. This is explained by less contamination of the limiter surface after removal of the boronisation layer from the limiter surface. On the basis of a simple 1D-impurity transport model a comparison of Langmuir and collector probe measurements with spectroscopic measurements in the core plasma was made, supporting this hypothesis.

Additional information

Authors: HILDEBRANDT D ET AL., Max-Planck-Institut für Plasmaphysik, Euratom Division, Berlin (DE)
Bibliographic Reference: Article: Journal of Nuclear Materials, Vol. 220-222 (1995) pp. 703-707
Record Number: 199510769 / Last updated on: 1995-07-12
Original language: en
Available languages: en
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